Method of and apparatus for handling magnetizable material



May 22, 1962 METHOD OF AND APPARATUS FOR HANDLING MAGNETIZABLE MATERIAL Filed Feb. 24, 1960 J. C. FOU REY a if 7-2-7? Z0 hf Z44 i g r\ i I I 30 26 IN VEN TOR. mzzzsdl fizr United States Patent 3,036,245 METHOD OF AND APPARATUS FOR HANDLING MAGNETIZAELE MATERIAL Jacques Christian Fourey, Fontainebleau, France, assignor to Preparation Industrielle des Cornbustibles, Fontainebleau, France, a French concern i Filed Feb. 24, 1960, Ser. No. 10,588 Claims priority, application France Feb. 27, 1959 7 Claims. (Cl. 317-123) This invention relates to material handling and has more particular reference to a method and apparatus for handling magnetizable materials.

It is old and well known to employ electromagnets for transporting magnetizable material, as for example, in unloading magnetite from a truck or railway car; The electromagnet is energized and attracts the material located in its magnetic field so that this material can be conveyed as a mass held by the eleotromagnet. However, this process has one great disadvantage for the material or particles thereof which are located at a distance from the armature of the electromagnet are ina magnetic field the intensity of which is much lower than that of the zone near the armature. There is, consequently, a risk that some of the magnetizable material will fall from the electromagnet during transportation, particularly so in the event of any mechanical shocks. For the purpose of clarity of description in the specification, such material or particles which are located, during transportation by the electromagnet, in a zone of low field intensity, are referred to as wavering.

To avoid the possibility of falling during transportation, the electromagnet 'is often fitted with a bucket, in one or two parts, which becomes located under the electromagnet when the latter has lifted its load to a certain level and accompanies the electromagnet to its discharge position. I i

This device is eflicient, but it has the disadvantage that it makes the handling unit heavier and more complicated and thus increases its cost. e

One object of the present invention is to provide a novel method of and apparatus for handling magnetizable material which eliminates or reduces the disadvantages described above. i

Another object of the present invention is to provide a novel method for handling magnetizable material which comprises lifting a load of the material on an energized electromagnet and increasing thevoltage applied to the electromagnet whereby wavering materials are subjected to a higher magnetic field intensity tending to prevent them falling from the lifted load.

Another object of the present invention is to provide novel and improved apparatus for handling mag'netizable material comprising an electromagnet, a circuitforen ergizing the electromagnet to lift a load of the material, and a voltage increase circuit for increasing the voltage applied to the lifted electromagnet to prevent wavering materials or particles of the lifted material from falling.

Other objects and advantages of the invention will ap-' pear in the specification when considered in connection with the accompanying drawing, wherein? The FIGURE of the drawing is awirin'g diagram showing one embodiment of a control circuit for an electromagnet constructed in accordance with the present invention;

The present invention provides anovel method and apparatus for handling magnetizable material as, for

' example, in unloading magnetizable material from trucks or freight cars and, in general, comprises the use of an electromagnet for lifting and transp orting the magnetizable material with provision for increasing the voltage applied to the electromagnet after the load has been lifted, to thereby subject the wavering material to a higher magice netic field intensity to prevent it from falling from the lifted load. The material handling method of the invention involves two stages. In the first stage, a predetermined normal voltage is applied to the electromagnet in order to establish a magnetic field of corresponding intensity and apply an attractive force to a load of the material beinghandled. When the electromagnet has been raised with its load, the second stage comes into effect, in which the applied voltage is increased, which raises the intensity of the magnetic field and so imposes a greater attractive force on the load to prevent even the remotest particles from falling during handling.

Referring now to the drawing, there is illustrated an electromagnet and circuits for controlling the energizing of the armature to provide, in sequence, two magnetic fields of different intensity, first for picking up a load of magnetizable material and then holding the picked up load with a stronger field to prevent loss from wavermg.

As there shown, the apparatus comprises an electromagnet 10, a rectifier 11, a double-coil transformer 12, and a low voltage transformer 13. The electromagnet it) may be of any suitable usual type and is connected to be supplied with direct current from the rectifier 11 which is connected to the terminals of the double-coil transformer 12. The double-coil transformer 12 is connected to the alternating current main supply line S through a contactor including contacts 14 and Is and a changeover switch including fixed contacts 16, 16 and 17, 17, and a movable contact 18. The low voltage transformer 13 is connected to the main supply line S and feeds through push button switch 19, a first control circuit, indicated generally at 23-, for controlling the creation of a magnetic field of average or normal intensity in the electromagnet, and a second control circuit, indicated generally at 21, for controlling the creation of a strong magnetic field in the electromagnet.

The first control circuit 20 comprises a push button switch 22, a coil 23 surrounding a core 24- connected at one end to the contacts 14-, 15 and at the other end to a contact 25 in a bypass line for the push button switch 22.

The second control circuit 21 comprises a push button switch 26, a coil 27 surrounding a core 28 connected at one end to the movable contact 18 and at the other end to a contact 29 in a bypassline for the push button switch 26. The first control circuit 20 feeds the second control circuit 21 through conductor 30.

The operation of the apparatus is believed obvious. When the electromagnet 10' is placed on or just above the stack or pile of magnetizable material to be transported, the push button switch 22 is pressed to complete a circuit from the transformer 13 through the switches 19 and 22 and a coil 23 surrounding the core 24 connected to the contacts 14 and'15. Energization of the coil 23 causes the contacts 14, 15 and also the contact '25 to close, the contact 25 being placed in parallel with the switch 22. Due to the closing of the contact 25, the coil 23 continues to be energized when the switch 22 opens. Since there is no current in the'coil 27 which surrounds the core 28 connected to the movable contact 18, and since this core is biased to the left as shown, the contact 18 remains in contact with the fixed contacts 16 and the current passesthrough all the primary coils of the transformer 12. A certain magnetic field is thus produced by the electromagnet 10.

The core 24 carrying the contacts 14, 15 and 25 is biased so that these contacts open when the coil 23 is not energized. Likewise, the core 28 carrying the contacts 1'8 and 29 is biased to open the contacts 29 and to move the contacts 18 onto the contacts 16 when the coil 27 is not energized.

The electromagnet is then lifted from the magnetizable material and carries a load under the attraction of the magnetic field, including wavering particles or material which are feebly attracted and tend to. fall.

The push button switch 26 is then closed to energize the coil 27 which closed the contact 29 for continuing energization of the coil 27 after the push button switch 26 opens, and also moves the movable contact (18 onto the fixed contacts 1'7 connected to a tapping 31 of the transformer 12. The current then passes only through this tapping 31 of the primary coil of the transformer 12, with the result that the secondary voltage increases and, therefore, the magnetic field intensity in the electromagnet 110 also increases. In this way, the voltage applied to the electromagnet 10 is increased after it has taken a load of material from the pile and the increased magnetic attraction holds the load more strongly and prevents the wavering particles or material from falling during transportation.

It should be noted that the circuit served by the push button switch 26 is only effective after the circuit controlled by the push button switch 22 has closed the contacts 14 and 15. In this way, even if the switch 26 were inadvertently operated, with the electromagnet 10 contacting the pile and before the switch 22 had been operated, the closing of the contacts 29 and change-over of the movable contact 17 has no effect, since the transformer 12 is disconnected from the main supply, be-

cause the contacts 14 and 15- are still open. The stronger magnetic field cannot, therefore, be produced, until the weaker field has already been established, so that even accidental operation of the switch 26 does not lead to the electromagnet 10 picking up a load under conditions in which its field intensity cannot be increased, which would otherwise produce the very problem solved by the invention.

To drop the material being conveyed, it is sufiicient to operate the push button switch 19 which stops the energization of the coils 213 and 27 and causes the contacts 14 and 15 to open and the contacts 18 to move back onto the contacts 16. The circuit is thus broken at the contacts 14 and 15 to deenergize the electromagnet 10 and change-over of the contacts 18 assures that the electromagnet 10 is energized by the reduced voltage when the switch 22 is again closed. 1

From the foregoing it readily will be understood that there has been provided a novel and improved method and apparatus for handling magnetizable material as, for example, in unloading magnetizable material from, trucks or freight cars comprising an electromagnet for lifting and transporting the magnetizable material with provision for increasing the voltage applied to the electromagnet after the load has been lifted to thereby subject the wavering material to a higher magnetic field intensity to prevent it from falling from the lifted load.

It will be clear that, without exceeding the scope of the invention as defined in the appended claims, other embodiments can be constructed dilferent from that described above. For example, instead of three push button switches, only two push button switches need be used if the closing of'the switch 26' were controlled by the lifting or the rotation of the electromagnet. It is also possible, at the time of unloading, to pass through the electromagnet, for a very short time, a current opposed to the normal one in order to facilitate and accelerate the unclogging of the material conveyed.

What is claimed is:

1. A method for handling magnetizable materials, which comprises supplying a predetermined normal voltage to an electromagnet to energize it for lifting a load of the material on the energized electromagnet and afterwards applying a higher voltage than said normal predetermined voltage to the lifted electromagnet to increase its magnetic field intensity, whereby wavering ma-' terials in the lifted load are subjected to a higher magnetic field intensity tending to prevent them falling from the lifted load.

2. Apparatus for handling magnetizable material comprising an electromagnet, a circuit for supplying a predetermined normal voltage for energizing the electromagnet to lift a load of material,and a circuit for supply ing a voltage higher than said predetermined normal voltage to the electromagnet after it has lifted a load of material, to increase the intensity of the magnetic field and prevent wavering material from falling from the lifted load.

I 3. Apparatus as set fo rth in claim 2, wherein a first control circuit serves to control the circuit for supplying a predetermined normal voltage to the electromagnet,

and a second control circuit serves to control the circuit for supplying a voltage higher than said predetermined for closing contacts in the circuit for supplying a prede- V termined voltage for energizing said electromagnet.

5. Apparatus as set forth in claim 4, wherein said second control circuit includes a push button switch serving to energize a coil, and a movable core having contacts.

thereon and being movable by energization of the coil for opening contacts in the circuit for supplying a predetermined normal voltage for energizing said electromagnet and substantially simultaneously closing contacts in the circuit for supplying a voltage higher than said predetermined normal voltage for energizingsaid electromagnet.

. 6. Apparatus as set forth in claim 5, wherein said movable core in said first control circuit carries a contact for bypassing the push button switch in said first control circuit upon release thereof and wherein said movable core in said second control circuit carries a contact for bypassing the pushbutton switch in said second cont-r01 circuit upon release thereof.

I 7. Apparatus as set forth in claim 6, wherein the push button switches in the first and second control circuits are normally resiliently held open and wherein a circuit is provided for supplying current to said control circuits including a normally resiliently held closed push button switch.

References Cited in the file of this patent UNITED STATES PATENTS 895,135 Wright Aug. 4, 1908 1,915,566 Younghusband June 27, 1933 Yorkey Sept. 30, 1941 

